Electromagnetic sound-producing device



Get. 20, 1931. .1. H. VAN WAGENE N ELECTROMAGNETIC SOUND PRODUCINGDEVICE Original Filed May 10, 1923 4 SheetS-Shz eec l PLATE OF AUDIOH-TO "B" BATTERY Snow How,

"A" sm-reav.

JAMES H. VAN WAGEHEN.

TO PLATE,

Oct. 20, 1931. J. H. VAN WAGENEN 1,827,919

ELECTROMAGNETIC SOUND PRODUCING DEVICE Original Filed May 10, 1923 4Sheets-Sheet 2 Oct. 20, 1931.

J. H. VAN WAGENEN ELECTROMAGNETIC SOUND PRODUCING DEVICE Origin al FiledMay 10, 1925 4 sheets-Sheet 5 JAMES H. ww WAGENEN.

1931- J. H. VAN WAGENEN 1,327,919

ELECTROMAGNETIC SOUND PRODUCING DEVICE Original Filed May 10, 1923 4 het 4 TO SOURCE OF VARYING CURREHTS.

gmentoz JAMES HVVAH WAGEHEH.

Patented Oct. 20, 1931 UNITED STATES PATENT oFFics James H. van WAGENEN,or wasmneron, ms'rmc'r or conumsm v ELECTROMAGNETIC SOUND-PRODUCINGDEVICE Application filed May 10, 1923, Serial No. 638,079. BenewefiApril 26, 1926.

This invention relates to apparatus for producing sound from a vibratingsound generator which is actuated by the armature or vibratory member ofan electromagnetic device.

One purpose'of my invention is to provide an electromagnetic actuatorhaving a responsive element capable of universal movement and which isfree from mechanical stresses and strains so that its movements are dueX is not confined to such apparatus, and is adapted to many other typesof electromagnetic mechanism.

In the accompanying drawings, I have illustrated several formsin whichthis invention may be embodied. Figure 1 shows one form.which isparticularly adapted for use in connection with the audio amplifyingcircuit of a radio receiving apparatus; Fig. 2 is a vertical sectionalView on the line 2-2 35. of Fig 1; Figs. 3, 4 and 5 are transversesectional views on the. lines 3-3, 4-4 and 5-5 respectively of Fig. 2;Figs. 6, 7, 8, 9, 10, 11, 12 and 15 illustrate various modifications ofthe invention; Fig. 13 is a vertical sectional view on the line 1313 ofFig. 12; Fig. 14 is a diagrammatic view showing the use of anelectromagnet instead of the permanent magnet shown in the otherfigures; Fig. 16 is a vertical sectional view on the line 1616 of Fig.15; and Fig. 17 shows one arrangement of mounting the sound-producingvibrating element within an amplifying chamber, such as a horn.Electromagnetic actuators universally em- 0 ploy an armature which ispivoted or is otherwise held by a rigid support, so that the armature ispermitted to move only in a prescribed manner. Such arrangements notonly confine the armature to certain predetermined movements but alsocause internal mechanical stresses therein, besides creating extraneousdisturbing influences. Even if the armature is suspended by a cord it isnot entirely free, being held from bodily movement in at least onedirection. I have found that an armature which is subjected to internalmechanical stresses will have an acoustic periodicity of its own, whichwill interfere with and distort the movements or vibrations of thearmature responsive to changes in the magnetic field controlling thesame, which varies .in response to variations in the electric currentsflowing in the energizing coil thereof.

In the embodiment of my invention illustrated inFigs. 1 to 5, theenergizing coil 20, which is connected to the auditory circuit or to anyother source of varying or intermittent currents, is held between curvedplates 21 seated in recesses within the pole-pieces 23 of a permanentmagnet 25 and clamped by screws 24. The central space within the coil isfilled by a block of any suitable elastic material 26, such as spongyrubber, cork etc. The armature consists of a magnetizable rod 27 and iscentrally held or suspended between the pole pieces by passing. throughthe block of elastic material. Fine adjustments that may be required toaccurately center the armature between the poles may be madeby means ofthe iron screws 28 which constitute adjustable portions of the polepieces. The elastic suspending or supporting medium permits the armatureto assume its natural position free from any rigid restraint, such as.would be imposed by. a spring suspension and therefore without anyinternal mechanical stresses and to move bodily in any direction or tovibrate in any manner in response to themagne'tic forces created by theenergizing currents flowingin the coil 20; and at the same time saidelastic suspending medium protectsthe armature from disturbing externalinfluences." Moreover, it servesto absorb and prevent anytendency tonatural 100 vibrations or acoustic periodicity inherent in any part ofthe structure. Inasmuch as there is no fixed pivot, the lateralvibrations of the armature will oscillate about a variable centerdetermined only by the resultant forces and which-may or may not be onthe central axis'of the magnet; that is to say, without confining theposition or location of a nodal point in the, armature it is renderedaperiodically sensitive or in other words uniformly sensitive andresponsive to all frequencies. The amplitude of vibration or amount ofmovement produced by the magnetic forces, may be regulated or damped toany desired degree by adjusting the screws 30, bearing upon the disk 31,to compress the elastic medium 26.

The electromagnetic vibrations of the armature are transformed intosound waves by connecting the rod 27 to a vibratable member which may bemade of paper, metal or other suitable material. Mounted on the.

rod 27 are adjustable clips 39 which are adapted to clamp one edge ofthe vibratable member 35.

The vibratable member 35 comprises 'a sheet that may be of any desiredshape and is'so. mounted as to have all edges thereofseries of notches36a into which the sheet 35 fits so as to retain the sheet in itspredetermined form. Thus, while the edges of the iheet are free tovibrate, the sheet is held ent.

It will be noted that the vibrations of the magnetic armature arecommunicated to the vibratable member 35 at the edge thereof so that thesound waves are propagated from the edge of the vibratable member towardthe center thereof and throughout the length of the sheet 35, withconsequent advantage in the reproduction of the sounds received in theelectromagnet.

In the modification shown in Fig. 6, the coil 20 is held in a frame orbracket 38,'secured to the upper side of the pole-pieces and 'to whichthe standard 36 is also attached.

The armature is supported for universal movement in the blocks ofelastic material 26 and 26", the latter being clamped betv' ,en plates21' which may be adjusted laterally to center the armature by means ofthe clamping screws 28' and may also be compressed if desired. In thisform the armature projects below the magnet and carries an adjustableclip 39 for attachment to the sound amplifier 35. Any of the structuresillustrated in the drawings herein may be enclosed in a cabinet havingone or more sides thereof ventilated to the open air. I have illustratedone such arrangement by doteand-dash lines in Fig. 6. The soundreproducer unit may be mounted in the cabinet in any suitable manner.

In Fig. 7 the sound amplifying sheet is clamped to an intermediate pointof the armature, one foot of the bracket 38 being omitted to permit thesheet to pass through. In the forms shown in Figs. 6 and 7, the armaturemoves bodily and freely in vibrating between the magnet poles.

Instead of using a flexible bowed sheet as the sound amplifier, thearmature may be connected directly to the diaphragm 40 of a soundproducing or amplifying horn 41 as indicated in Fig. 8. Again the bowedsound producing sheet may be enclosed in an amplifying horn 42 and mayconform more or less to the contour of the resonance chamber 42* whenthe horn is so constructed, as. indicated in Fig. 17.

In order that the coil may closely surround the armature, the coil 20may be placed within a recess in the elastic cushioning medium 26, inthe manner illustrated in Fig. 9.

In the arrangement shown in Fig. 10, the coil 20 is embedded in theelastic block 26 and is wound directly upon the armature;

rod 27 may be replaced by a rod of wood,

brass or other light material Which serves merely-to transmit thevibrations of the coil to the amplifying sheet 35, the energizing coil20 being thus free to vibrate in the elastic mass 26, and therebyconstituting also the 'vibrating armature.

In Fig. 11, the actuatlng coil 20 is carried by thepole-piece 23 and thearmature 27 is carried by the pole-piece 23 the latter being angularlyadjustable by means of the screws 33, to thereby adjust the armaturetoward or from the pole-piece 23. An arm 27 of any suitable lightmaterial attached to the armature, passes through the cushioning block26, supported by the adjusting screw 46, and carries the clips 39 forattachment to the sound amplifying sheet 35.

In the arrangement shown in Fig. 12, the lower end of the armature isembedded in a block of cushioning material carried by a box 48 slidablymounted on the lower polepiece and provided with an adjusting screw 46.I have also shown in this figure that a plurality of bowed soundcreating or amplifying sheets 35 may be connected to armature. A furthermodification is illustrated in Fig. 15 in which the armature consists ofthe coil 20 connected to the source of varying currents,indicatedconventionally by the trans- The actuating coil 20,constituting the movable element, may be attached to a spool or disk 57,having a stem 58 upon which a. nut

' 59 is threaded, for the purpose of clamping the coil to a disk 60 ofelastic material, such as cork, sponge rubber etc. The disk 60 may beheld by a sleeve 61 surrounding the magnet, the position of the coil 20being determined by the thickness of aninterposed nonmagnetic ring rod27 of any suitable light material is attached at an intermediate pointto the end of the stem 58, the rod passing through'a block 26 of elasticmaterial and having its lower end anchored in another block 26' ofelastic material. The position of the coil 20 can be adjusted by meansof the screw 28*. All of the parts of the .moving element may beconstructed of very light material which will transmit vibrations to theamplifying bowed sheet 35, in response to exceedingly feeble currentsflowing in the coil 20.

I have shown the amplifying sheet attached by clip 39 directly to theactuator rod of the apparatus, but it will be evident that the free endof the sheet may be attached to a suitably supported vibratory member,which in turn is vibrated by said actuator rod. Or

the amplifying sheet may be attached directly to the stem 59, theparticular manner of connecting the sheet to the actuating memberdepending upon the degree of amplitude of I vibration desired.

I claim 1. An electro-magnetic actuator for sound reproducing apparatuscomprising a magnet, a magnetizable member so positioned within themagnetic field of said magnet as to permit vibratory movementstransverse to the longitudinal axis of said member, an elasticcushioning medium in which said member is .floatingly disposed Withoutconfining the position of a node therein, and an energizingcoilsurrounding said member and operating to vary the stresses exertedthereon to thereby cause said vibratory movements of said member in saidelastic medium,

2. In a device as set forth in claim 1, means for varying the degree offlexibility of said elastic medium.

3. A device as set forth in claim 1, and a flexible vibratory soundproducing device ,operatively connected to said member.

4. An apparatus as set forth in claim 1, and means for adjusting thepole-pieces of said magnet toward or from said member.

5. An electroemagnetic actuator, comprisinga magnet, a magnetizablemember so pofsitioned vwithin the magnetic field of said magnet as topermit vibratory movements free vibrations floatingly supporting thesame, and an energlzing coil actuating said member and operating to varythe magnetic flux Within the field of said magnet to thereby cause saidmovements of said member.

6. An electro-magnetic actuator, comprising a magnet, a member sopositioned as to permit of oscillatory v movements of said member,an-elastic cushioning medium supporting said member, and means operatingto vary the magnetic flux within the field of said magnet to therebycause said movements of said member.

7. A sound reproducing device comprising a membrane and a soundreproducing member attached tangentiallyto one edge of said member toimpart vibrations tangentially to the plane thereof, said membrane beingarcuate within the range of 90 whereby the edge opposite said one edgeis free to vibrate.

8. A sound reproducing device comprising an arcuate membrane of at least90 and a sound reproducing member attached tangentially thereto toimpart vibrations to the marginal-edge thereof,

9. A sound reproducing device comprising a flexed membrane completelyexposed to surrounding atmosphere whereby said. membrane acts as adirect sound radiator and a sound reproducing member attachedtangentially to the marginal edge thereof.

as a direct sound radiator flexed to form a portion of a cylinder and asound reproducing member attached tangentially to the marginal edgethereof.

11. A sound reproducing device compris- 'a cylinder, and a soundreproducing member attached tangentially to. the marginal edge thereof,the supported edge of said mem brane opposite the marginal edge beingfree to vibrate,

14. A-sound reproducing device comprisingza membrane fixed at at leastone edge thereof and flexed to ,form a portion of a cylinder, and a fullfloating sound reproducing member attached tangentially thereto toimpart vibrations tangentially to the plane thereof.

15. A sound reproducing device comprising a membrane and anelectro-magnetically operated sound reproducing member attachedtangentially tothe marginal edge thereof, the edge of said membraneopposite the marginal edge being free to vibrate.

16-. A sound reproducing device comprising a membrane and anelectro-magnetically operated full floating sound reproducing memberattached tangentially thereto to impart vibrations tangentially to theplane thereof. I I

17. A sound reproducing device comprising a flexed membrane and anelectro-magnetically operated full floating sound reproducing memberattached tangentially to the marginal edge thereof. 18. A soundreproducing device comprising a flexed membrane and an electro-magnetically operated full floating sound reproducing member attachedtangentially thereto to impart vibrations tangentially to the planethereof,

19. A sound reproducing device comprising a membrane and a soundreproducing member attached tangentially to the marginal edge thereof,and a frame for supporting said membrane and member cushioning mediumfor floatingly mounting the membrane so that free vibrations aresubstantially damped.

A 20. A sound reproducing device comprising a membrane and a soundreproducing member attached tangentiallyto the marginal-edge thereof,and a frame for supporting said membrane and member, said frame alsoserving to act as a sounding board to reinforce the air vibrations setup by the membrane and an elastic cushioning medium for floatinglymounting the membrane so that free vibrations are substantially damped.

21. A sound reproducing device comprising a flexed membrane and a fullfloating sound reproducing member attached tangentially thereto toimpart vibrations tangentially to the plane thereof, and a frame forsupporting said membrane and member.

22,, A sound reproducing device comprising a vflexed membrane and afull. floating sound reproducing member attached tangentially thereto toimpart vibrations tangentially to the plane thereof, and a frame forsupportingsaidmembrane and member, said frame also serving to act as asounding board to reinforce the air vibrations set up by the membrane.

23. A sound reproducing device compri ing a membrane fixed at at leastone edge thereof and a full floating sound reproducing member attachedtangentially to the marginal edge thereof, and a frame for supportingsaid and an elastic membrane and member, said frame also serving to actas a sounding board to reinforce the air vibrations set up by themembrane.

24. A sound re roducing device comprising a flexed membrane fixed at atleast one edge thereof, and a sound reproducing member attachedtangentially to the marginal edge thereof, and a frame for supportingsaid membrane and member and an elastic cushioning medium for floatinglymounting the membrane so that free vibrations are substantially damped.

25. A sound reproducing device comprismodulations of said current, avibratile sound reproducing medium, means for connecting the armatureto' said medium at one edge thereof and means for applying a tension tosaid medium. i

27. In an electrical acoustical device the combination comprising anelectromagnet adapted to be actuated by a modulated electric current, afull-floating electromagnetic armature vibrated in accordance with themodulations ofsaid current, a vibratile sound reproducing medium, saidconnection being off the center of said medium, and means for applying'atension to said medium.

28. In an electrical acoustical device the combination comprising anelectromagnet adapted to be actuated by a modulated electric current, afull-floating electromagnetic armature vibrated in accordance with themodulations of said current, a vibratile sound reproducing medium ofnon-circular shape, means for connecting the armature to said medium,and means for applying a tension to said medium.

29. In an electrical acoustical device the combination comprising anelectromagnet adapted to be actuated by a modulated electric current, afull-floating electromagnet armature vibrated in accordance with themodulations of said current, a vibratile sound reproducing medium ofgreater length than width and non-conical in shape, means for connectingthe armature to said medium and means for applying a tension to saidmedium.

30. In an electrical acoustical device the combination comprising anelectromagnet adapted to be actuated by a modulated electric current, afullfloating electromagnetic armature vibrated in accordance with themodulations of said current, a vibratile sound reproducing medium, meansfor connecting the armature to said medium, means for connecting thearmature to said medium so that the vibrations of said armature arecaused to progress toward the center of said medium.

31. In an electrical acoustical device the combination comprisin anelectromagnet adapted to be actuated by sition of a node therein andvibrated in accordance with the modulations of said current, avibratilesound reproducing medium, means for connecting the armature to saidmedium and;means for mounting said medium so that all edges thereof arefree and unsupported. a

32'. In an electrical acoustical device the combination comprisinganelectromagnet adapted to be actuated a modulated electric current, anelectromagnetic armature vibrated in accordance with the modulations ofsaid current, a vibratile sound reproducing medium, means for connectingthe armature to said medium, at one'edge thereof and adjustable meansfor applying a tension to said medium and mounting said soundreproducing mediumin a cushioning means for substantially g'damping anyfree vibra tions.

33. In an electrical acoustical device the combination comprising anelectromagnet adapted to be actuated by a modulated electric current, anelectromagnetic armature resiliently supported without fixing theposition of a node therein and, vibrated in accordance with themodulations of said our- 1 rent, a vibratile sound reproducing medium,

means for connecting the armature to said medium at. one'edge thereof,means for applying a tension to said medium and a ventilated enclosurein which the electromagneti cally actuated medium is mounted andmounting said sound reproducing medium in a cushioning means forsubstantially damp.- ing any free vibrations.

34. In an electrical acoustical device the combination comprising anelectromagnet adapted to be actuated by a modulated electric current, anelectromagnetic armature resiliently supported without fixing theposition of a node therein and vibrated in accordance with themodulations ofsaid current, a vibratile sound reproducing medium ofgreater length than width and non-conical in shape, means for connectingthe armature to said medium, means for applying a tension to said mediumand a ventilated enclosure in which the electromagnetically actuatedmedium is mounted and mounting said sound reproducing medium in acushioning means for substantially damping'any free vibrations.

35. In an electrical acoustical device the combination comprising anelectromagnet a modulated elec-; tric current, an electromagneticarmature resiliently supported without fixing the poadapted to beactuated by a modulated electric current, an electromagnetic armaturevibrated in accordance with the modulations -of said current, aplurality of vibratile sound reproducing mediums, means for connectingthe armature to said mediums at the edges thereof and means for applyinga tension to said mediums and mounting-said sound reproducing medium ina cushioning means for substantially damping any free vibrations.

36. A sound reproducing device comprising a membrane and an electricallyoperated sound reproducing member attached tangentially thereto toimpart vibrations tangentially to the plane thereof, the edge of saidmembrane opposite the attached edge being free to vibrate.

37. A sound reproducing device comprising a membrane and a full floatingelectrically operated sound reproducing member attached tangentiallythereto to impart vibrations to the margmal edge thereof.

38. A sound reproducing device comprising a flexed membrane and a fullfloating electrically operated sound reproducing ing a membrane fixed atat least one edge thereof, and a full floating electrically operatedsound reproducing member attached tangentially to the marginal edgethereof.

42. A sound reproducing device comprising a membrane fixed at at leastone edge thereof, and a full floating electrically operated soundreproducing member attached tangentially thereto to impart vibrationstangentially to the plane thereof.

4 43. A sound reproducing device comprising a membrane fixed at at leastone edge thereof and flexed to form a portion of a cylinder, and a fullfloating electrically operated sound reproducing member attachedtangentially to the marginal edge thereof.

44. A sound reproducing device comprising a membrane fixed at at leastone edge thereof and flexed to form a ortion of a cylinder, and a fullfloating e ectrically operated sound reproducing member attached.

tangentially thereto to impart vibrations tangentially to the planethereof.

45. In an-acoustical device the combination comprising a stationarymagnet, a conductor responsive to modulated current juxtaposed to thecore of the magnet, non metallic resilient means for supporting saidconductor at a normal predetermined position with respect to said core,a vibratile membrane, and means to connect the conductor tangentially tothe membrane.

46. In an acoustical device the combination comprising a stationarymagnet, a conductor responsive to modulated current juxtaposed to thecore of the magnet, a membrane, resilient means enclosing the conductorand forming the sole support therefor and maintaining the conductor at anormal predetermined position 'with respect to said magnet, and

means to connect the conductor tangentially to the membrane.

47. In an acoustical device the combination comprising a stationarymagnet, a conductor responsive to modulated current juxtaposed to thecore of the magnet, resilient means for supporting. said conductor incompressed equilibrium at a normal predetermined position with respectto saidcore, a vibratile membrane andmeans to connect the conductortangentially to the membrane, and means to adjust the-normal position ofthe conductor.

48. In an acoustical device the combination comprising a stationarymagnet a conductor responsive to modulated current juxtaposed to thecore of the magnet, resilient means enclosing the conductor and formingthe sole support therefor and maintaining the conductor at a normalpredetermined position with respect to said magnet, means to connect theconductor tangentially to the membrane andv means to adjust the normaposition of the conductor.

49. An actuator for sound reproducing devices comprising a memberresponsive to electrical'impulses so positioned in a magnetic field asto be oscillated thereby, an elastic cushioning medium retaining themember in adjustable position and forming the sole support thereforwithout fixing the cen ter of oscillation of said member.

50. A method of increasing the sensitivity of a member subjected tooscillation under the action of a variation in magnetic flux comprisingfloatingly mounting the member in a flexible medium without fixing acenter of oscillation.

51. A method of increasing the sensitivity of a member subjected tooscillation under the action of a variation in magnetic flux comprisingfloatingly mounting the member in a variable resilient medium therebyinsuring freedom to the variable positioning of the oscillatory centerof said member.

52. A method .of increasing the sensitivity of an oscillating memberwhich is movable in response to sounds comprising floatingly mountingthe member in a resilient medium and thereby insuring freedom to thevariable I 53. An actuator for sound reproducing de-.

vices comprising a member subjected to and displaceable in response tovariations in elec- ,trical energy in its field of action, and aresilient mounting for the member adapted to floatingly mount the memberand thereby insuring freedom to'the variable positioning of the centerof displacement of said member.

54. A method of transforming electrical vibrations into sound vibrationscomprising transforming the electrical vibrations into proportionatemechanical movements without utilizing a fixed pivot during suchmovements, impressing such movements upon an initially substantiallycylindrically flexed member to vary the flexure thereof andcorrespondingly displace the adjacent medium.

' 55. An electromagnetic actuator for sound reproducing apparatuscomprising a magnet, a magnetizable member so positioned within themagnetic field of said magnet as to permit vibratory movementstransverse to the longitudinal axis of said member, an elasticcushioning medium in which said member is partially embedded and formingthe sole support therefor without fixing the position of a node therein,and an energizingcoil associated with said member and operating to varythe stresses exerted thereon to thereby cause said vibratory movementsof said magnetizable member. A

56. In a device as set forth in claim 55, means for varying the degreeof flexibility'of said elastic medium.

57. A device as set forth in claim 55, and a flexible vibratory soundproducing device operatively connected to said member.

58. An apparatus as set forth in claim 55, and means for adjusting thepole pieces of said magnet toward or from said member.

59. An electro-magnetic actuator, comprising a magnet, an oscillatorymagnetizable member so positioned within the magnetic field of saidmagnet as to permit vibratory movements transverse to the longitudinalaxis of said member, anelastic cushioning medium forming the solesupport for said member, and an energizing coil actuating said memberand operating to vary the magnetic flux within the field of said magnetto {)hereby cause said movements'of said mem- 60. An electro-magneticactuator, comprising va magnet, a member so positioned as to permitoscillatory movements, an elastic cushioning medium forming the solesupport for said member, and means operating to vary the magnetic fluxwithin the field of said magnet to thereby cause said movements of saidmember.

61. An electric translating device comprising an oscillatory elementsubject to mechanical impulses corresponding to sound viing the supportfor said element and a cush loning medium for said element withoututilizing a fixed pivot in said element.

63. The method of increasing the sensitivity of an electrically actuatedoscillatory member comprising disposing the memberwithin a resilientmedium thereby establishing freedom of position of the center ofoscillation of said member.

64. A method of increasing the fidelity of sound reproduction in which amember is vibrated in accordance with impressed vibrations whichcomprises floatingly mounting the member in a resilient medium andthereby establishing a variable center of oscillation of the member anddamping all the natural vibrating characteristics of the member andlargelyabsorbing extraneous vibrations. I

. which comprises vibrating the member in accordance with sounds, andmounting said member in cooperative relation with a restrictive mediumwhereby all its free vibrations are substantially damped;

66. The method of operating a. member which comprises vibrating themember in accordance with sounds, and counting saidmember in cooperativerelation with a' resilient cushioning means whereby its free vibrationsare substantially damped 67. The method of operating a member whichcomprises vibrating the member in accordance with the sounds in amagnetic field, and mounting said member in cooperative relation with arestrictive medium whereby its free vibrations are substantially damped.

68. In combination; an armature, an elec tromagnet, said armature beingpositioned in a magnetic field of said electromagnet and a medium inwhich the main portion 0t said armature is mounted fordamping thenatural vibrations of said armature.

69. In combination; a magnet, an arma- 65. The method of operating amember ed in said restrictive mediumwhereby the natural vibrations ofsaid armature are damped, and a vibratory sound producing deviceoperatively connected to said armature.

In testimony whereof I aflixmy signature.

JAMES H. VAN WAGENEN.

' dium, the body of said armature being mountture, a coil in codperativerelation with said armature and said magnet, a restrictive medium, themain portion of said armature being mounted in said restrictive mediumdrum.

70. In combination; a magnet, an arma-- ture, a coil in cooperativerelation with said armature and said met, a restrlctlve me.-

- ize

